Test plate for ceramic surface mount devices and other electronic components

ABSTRACT

A test plate for holding miniature electronic circuit components on a component testing system as a part of batch processing for parametric testing purposes, including passive, two-terminal, ceramic capacitors, resistors, multilayer inductors, inductor beads, varistors, thermistors, fuses, sensors, actuators, and the like, or another type of device under test (DUT), includes a DUT-holding plate having an upper side, a lower side, and a rotational axis. The DUT-holding plate defines a plurality of DUT-engaging holes extending through the DUT-holding plate from the upper side to the lower along central axes of the DUT-engaging holes that are not parallel to the rotational axis. With the DUT-holding plate oriented so that the rotational axis is not vertical, the DUT-engaging holes change orientation relative to vertical as they orbit the rotational axis. According to a separate aspect, the DUT-holding plate includes upper and lower layers that are bonded together to form the DUT-holding plate. The lower layer defines vacuum passageways for coupling a vacuum source on a vacuum plate portion of the component testing system in fluid communication with each of the DUT-engaging holes. The lower layer is fabricated to include the vacuum passageways and then it is attached to the upper layer in order to enable use of circuit board fabrication techniques instead of machine shop type operations.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] This invention relates generally to the batch processing of miniature electronic circuit components, including passive, two-terminal, ceramic capacitors, resistors, inductors, and the like. More particularly, it concerns a test plate for holding such components or other type of device under test (DUT) as part of the batch processing for purposes of parametric testing.

[0003] 2. Description of Related Art

[0004] The tiny size of electronic circuit components of interest herein complicates processing. Typically fabricated in parallelepiped shapes having dimensions as small as 0.020″ by 0.010″ by 0.010″ more or less, these difficult-to-handle components require appropriate equipment and precision handling techniques. What is sometimes referred to as a “carrier plate” holds many hundreds of the components upright in spaced-apart positions as the ends of each component are coated with a conductive material to produce electrical terminals. After adding terminals, a “test plate” holds the large batch of components for movement past a contactor assembly of a testing system for parametric testing purposes and eventual sorting. Thoughtful design of each of these components promotes efficient processing. Reference may be made to U.S Pat. Nos. 6,204,464; 6,294,747; 6,194,679; 6,069,480; 4,395,184; and 4,669,416 for examples of some prior art component handling systems and testing techniques.

[0005] The test plate is of particular interest. Mechanically, the test plate must hold the DUTs securely enough as they move past the contactor assembly so that they are presented to the contactor assembly in a repeatable, mechanically stable position. Electrically, the test plate must not degrade test results. But the mechanical and electrical functions are conflicting. Various forms of grease, grime, dirt, dust and other electrically conductive material on the test plate and/or on the DUTs provide unwanted conductive paths (i.e., stray impedances) to the DUT terminals. The stray impedances can render test results inaccurate. U.S. patent application Ser. No. 10/126,004 filed Apr. 14, 2002 describes a test plate that alleviates some of those specific concerns. But manufacturers engaged in batch processing of miniature electronic circuit components still seek additional test plate innovation to make the test more functional, efficient, and less expensive to fabricate.

SUMMARY OF THE INVENTION

[0006] It is an object of this invention to overcome additional short comings and disadvantages of prior art test plates in order to achieve more function, efficiency, and/or cost reduction. This is accomplished in part by providing a test plate having inclined DUT-engaging holes. Each hole extends along a central axis of the hole that is not parallel to the rotational axis of the test plate. As a result, with the test plate positioned so that the rotational axis is inclined, the DUT-engaging holes change orientation relative to vertical as the test plate rotates and the DUT-engaging holes orbit the rotational axis. At some positions, the holes are more vertically disposed and that facilitates movement of a batch of DUTs into the holes under influence of gravity. At other positions, the holes are more horizontally disposed and that facilitates movement of the DUTs out of the holes without working against gravity. Moreover, the slanted holes result in chamfer-like entrances to the DUTs so that the fabrication step of machining a chamfer on the upper lip of each hole can be avoided.

[0007] To paraphrase some of the more precise language appearing in the claims, a test plate constructed according to the invention includes a DUT-holding plate having an upper side, a lower side, and a rotational axis. The DUT-holding plate may be a single layer or a multiple layer plate with or without one or more guard layers. It defines a plurality of DUT-engaging holes that extend through the DUT-holding plate from the upper side to the lower side. Each of the DUT-holding holes has a central axis that extends between the upper side and the lower side. According to a major aspect of the invention, each of the holes is so disposed that the central axis of each hole is not parallel to the rotational axis.

[0008] According to a separate aspect of the invention, there is provided a test plate for use atop a vacuum plate portion of a component testing system. The test plate includes upper and lower layers that are bonded together to form a DUT-holding plate having an upper side, a lower side, and a rotational axis. The DUT-holding plate defines a plurality of DUT-engaging holes that extend through the DUT-holding plate from the upper side to the lower side. The upper layer defines an upper section of each of the DUT-engaging holes that provides a close fit for a DUT, while the lower layer defines a plurality of vacuum passageways that function as means for coupling a vacuum source from the vacuum plate portion of the component testing system to the plurality of DUT-engaging holes. Preferably, the lower layer includes first and second lower sub-layers that are bonded together to form the lower layer so that the second lower sub-layer defines a second segment of the lower section of each DUT-engaging hole that provides a close fit for a DUT in order to help support the DUT, while also defining a second segment of each vacuum passageway such that the second segments of the vacuum passageways are spaced apart from the DUT-engaging holes.

[0009] Although some existing test plates have vacuum passageways, they are machined into the bottom of the test plate after the rest of the test plate is fabricated. With separate layers, the vacuum passageways can be formed in the lower layer before the layers are bonded together and that simplifies fabrication, permitting use of circuit board fabrication types of fabrication techniques. In addition, the lower layer of one embodiment includes first and second sub-layers that are bonded together to form the lower layer. The first sub-layer defines a first segment of each of the plurality of vacuum passageways such that each first segment is in fluid communication with a respective one of the DUT-engaging holes. The second sub-layer defines a second segment of each of the plurality of vacuum passageways that couples the vacuum source from the vacuum plate portion of the component testing system to a respective one of the first segments. That way, the second layer can also define a portion of each of the DUT-engaging holes that provides a close, supportive fit for a DUT.

[0010] Thus, the invention provides a test plate that achieves more function, efficiency, and/or cost reduction. The following illustrative drawings and detailed description make the foregoing and other objects, features, and advantages of the invention more apparent.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 of the drawings is a top plan view of a first test plate constructed according to the slanted-hole aspect of the invention;

[0012]FIG. 2A is a diagrammatic view of the first test plate mounted at a forty-five degree angle on a component testing system;

[0013]FIG. 2B is a diagrammatic view of the first test plate after it is rotated about the rotational axis 180 degrees from the position shown in FIG. 2A;

[0014]FIG. 3 is an enlarged cross sectional view of a portion of the first test plate showing the orientation of one of the DUT-engaging holes, as view in a vertical plane bisecting the DUT-engaging hole;

[0015]FIG. 4 is an exploded view of a second test plate that is constructed according to the slanted-hole aspect of the invention to include multiple layers sandwiched together;

[0016]FIG. 5 is an isometric view of a third test plate that is constructed according to the vacuum-passageway aspect of the invention, showing its relationship to other structure on the component testing system;

[0017]FIG. 6 is a cross sectional view of a portion of a prior art test plate, as viewed in a vertical plane bisecting a vacuum passageway in the prior art test plate, together with an enlarged detail of a portion of the lower side that shows vacuum passageway orientation relative to a DUT-engaging hole in the prior art test plate;

[0018]FIG. 7 is an enlarged cross sectional view of a portion of the third test plate, as viewed in a vertical plane bisecting a vacuum passageway in the third test plate, together with an enlarged detail of a portion of the lower side that shows vacuum passageway orientation relative to a DUT-engaging hole in the third test plate;

[0019]FIG. 8 is an enlarged cross sectional view of a portion of the third test plate (similar to FIG. 7) that includes a DUT in the DUT-engaging hole;

[0020]FIG. 9 is an enlarged cross sectional view of a portion of a fourth test plate that is constructed according to the vacuum-passageway aspect of the invention to include a lower layer formed by first and second lower sub-layers that are sandwiched together; and

[0021]FIG. 10 is a further enlarged cross sectional view of a portion of a fifth test plate that is constructed according to the vacuum-passageway aspect of the invention to include an upper layer formed by first, second, and third upper sub-layers sandwiched together.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022]FIGS. 1, 2A, 2B, and 3 of the drawings show various aspects of a test plate 10 constructed according to the invention. Generally, the test plate 10 includes a DUT-holding plate 11 that defines an array (a plurality) of DUT-receiving holes 12, just one such DUT-receiving hole 12 being identified in FIGS. 1-3 for illustrative convenience. The illustrated test plate 10 includes four hundred, circularly shaped, DUT-receiving holes 12 arranged in four radially spaced apart, concentric rings of one hundred, circumferentially spaced apart holes each. Of course, the number, shape, and pattern of the holes can vary without departing from the inventive concepts disclosed.

[0023] With a batch of DUTs in the DUT-receiving holes 12, the test plate 10 serves the function of holding the batch of DUTs for movement past a contactor assembly on a component testing system 13 (FIGS. 2A and 2B) as described in U.S. patent application Ser. No. 10/126,004. That patent application is hereby incorporated herein by reference for all the information provided. In addition, U.S. patent application Ser. No. 10/097,464 provides details of a contactor assembly and its operation in the testing system, and that patent application is also incorporated herein by reference for all the information provided. Some details of prior art test plates and component testing systems are described in the U.S. Pat. Nos. 6,204,464; 6,294,747; 6,194,679; 6,069,480; 4,395,184; and 4,669,416 mentioned previously.

[0024] The DUT-holding plate 11 includes an upper side 14 (FIGS. 1-3), a lower side 15 (FIGS. 2A, 2B, and 3), and a rotational axis 16 (FIGS. 1, 2A, and 2B). The details of each of the DUT-engaging holes 12 are similar and so only the DUT-engaging hole 12 identified in the FIGS. 1-3 is described in detail. It extends through the DUT-holding plate 11 between the upper and lower sides 14 and 15 along a central axis 17 of the DUT-holding hole 12 (FIGS. 2A, 2B, and 3). According to a major aspect of the invention, the central axis 17 is not parallel to the rotational axis 16. It is inclined.

[0025] With the test plate 10 mounted on the component testing system 13 so that the rotational axis 16 is not horizontal or vertical (e.g., inclined forty-five degrees relative to vertical as illustrated in FIGS. 2A and 2B), the DUT-holding hole 12 and its central axis 17 change orientation relative to vertical as the test plate 10 rotates and the DUT-engaging hole 12 orbits the rotational axis 16. At some positions, the holes are more vertically disposed and that facilitates movement of a batch of DUTs into the holes. At other positions, the holes are more horizontally disposed and that facilitates movement of the DUTs out of the holes.

[0026]FIG. 2A illustrates the hole 12 at its lowermost position. In that position, the central axis 17 is vertical. FIG. 2B illustrates the hole 12 at its uppermost position. In that position, the central axis 17 is horizontal. Those orientations result because the central axis 17 is inclined forty-five degrees relative to the rotational axis 16. Of course, the hole 12 can be otherwise oriented relative to the rotational axis 16, at any angle in the range of one degree to eighty-nine degrees. The orientation of the central axis 17 relative to vertical at the lowermost and uppermost positions of the hole 12 is determined accordingly.

[0027] As suggested by FIG. 3, the DUT-holding plate 11 of the test plate 10 is a single layer. It may include multiple layers, however, within the scope of some of the broader claims subsequently presented. FIG. 4 illustrates a second test plate 100 having a rotational axis 116 and four layers 101, 102, 103, and 104. The four layers 101-104 define slanted DUT-engaging holes (just the uppermost portion of one hole 112 being identified). Other than the slanted DUT-engaging holes, the test plate 100 is generally similar to the multilayer test plate illustrated in FIGS. 1-6 of the U.S. patent application Ser. No. 10/126,004 mentioned previously. Based upon the foregoing and subsequent descriptions, one of ordinary skill in the art can readily implement a test plate constructed according to the slanted-hole aspect of the invention.

[0028] Turning now to FIG. 5, it shows a third test plate 200 that is constructed according to the vacuum-passageway aspect of the invention. It is similar in many respects to the other test plates, and it includes an array of DUT-engaging holes (slanted or not slanted). Just a single hole 212 is identified for illustrative convenience. The test plate 200 is illustrated in its usual environment, with a turntable 201 of a component system (such as the component testing system 13 in FIG. 2A), a vacuum plate 202, and upper and lower contactor assemblies 203 and 204 that operate to electrically contact terminals on DUTs in the DUT-engaging holes (not shown) as the test plate 200 rotates.

[0029] The vacuum plate operates in conjunction with the test plate 200 in a known way to couple a vacuum source (not shown) on the component testing system to the DUT-engaging holes in the test plate 200. It does this in cooperation with the test plate 200 inasmuch as the test plate 200 defines a vacuum passageway that couples the vacuum plate in fluid communication with the DUT-engaging holes.

[0030] Before examining the vacuum passageways of the test plate 200, consider a prior art test plate 250 illustrated in FIG. 6. It includes a DUT-holding plate 251 having an upper side 252 and a lower side 253. The DUT-holding plate 251 defines an array of DUT-engaging holes, including the one DUT-engaging hole 254 shown in FIG. 6. The DUT-holding plate 251 also defines a vacuum passageway 255 in the under side 253 that operates to couple a vacuum plate (such as the vacuum plate 202 in FIG. 5) to the DUT-engaging holes in the test plate 251, including the hole 254. The vacuum passageway 255 is machined into the under side 253 after the DUT-holding plate 251 is otherwise fabricated. A plan view of the underside 253 appears as an encircled detail portion of FIG. 6 to further show the relationship of the slot-shaped vacuum passageway 255 and the DUT-engaging hole 254.

[0031] Next, consider FIG. 7. It is a view similar to FIG. 6 that shows further details of the test plate 200 related to the vacuum-passageway aspect of the invention. The test plate 200 includes a DUT-holding plate 201 having an upper side 202 and an under side 203. The DUT-holding plate 201 defines an array of DUT-engaging holes, including the one DUT-engaging hole 204 illustrated and identified in FIG. 7. In addition, the DUT-holding plate 201 defines a vacuum passageway 205 that functions as means for coupling a vacuum source from a vacuum plate portion of a component testing system to the DUT-engaging holes.

[0032] According to the vacuum-passageway aspect of the invention, the DUT-holding plate 201 includes an upper layer 206 and a lower layer 207 that are bonded together. They are bonded together after the DUT-engaging hole 204 is formed in the upper layer 206 and the vacuum passageway 205 is formed in the lower layer 207. A plan view of the underside 203 appears as an encircled detail portion of FIG. 7. The layered structure results in significantly less fabrication time and expense in forming the vacuum passageway 205. Stated another way, printed circuit board types of fabrication techniques (i.e., forming holes and vacuum passageways before bonding the layers together) can be used instead of requiring machine shop type techniques (i.e., machining the vacuum passageways after the DUT-holding plate has been formed). In terms of the fabrication methodology employed, the method proceeds by providing upper and lower layers as described that have the DUT-engaging holes and the vacuum passageways formed in them. The method proceeds by boding the upper and lower layers together to form the DUT-holding plate. Based upon the foregoing and subsequent descriptions, one of ordinary skill in the art can readily implement a test plate constructed according to the vacuum passageway aspect of the invention.

[0033]FIG. 8 shows the test plate 200 with a DUT 210 in the DUT-engaging hole 204. FIG. 8 is intended to indicate a close fit of the DUT 210 within the portion of the DUT-engaging hole 204 in the upper layer 206. This provides support that helps secure the DUT 210 in position. Notice that the lower portion of the DUT 210 within the vacuum passageway 205 is not supported.

[0034]FIG. 9 shows a fourth test plate 300 constructed according to the vacuum passageway aspect of the invention. It is generally similar to the test plate 200, having a DUT-holding plate 301 with upper and lower layers 306 and 307 that define a DUT-engaging hole 304 in which a DUT 310 is positioned. The lower layer 307 also defines a vacuum passageway 305. The dashed line depicts the vacuum path. The primary difference in the test plate 300 is that the lower layer 307 includes an upper first sub-layer 307A and a lower second sub-layer 307B that cooperatively define the vacuum passageway. That arrangement permits use of the second sub-layer 307B to define a lower portion 304B of the DUT-engaging hole 304 so that it provides a close supportive fit for the DUT 310.

[0035]FIG. 10 shows a fifth test plate 400 constructed according to the vacuum passageway aspect of the invention. It includes a DUT-holding plate 401 having an upper and lower sides 401A and 401B together with upper and lower layers 406 and 407 that define a DUT-engaging hole 404 in which a DUT 410 is positioned. The lower layer 407 includes first and second sub-layers 407A and 407B that cooperatively define a vacuum passageway having a first section 405A in the first sub-layer 407A and a second section 405B in the second sub-layer 407B. In addition, the second sub-layer 407B defines a lower portion 404B of the DUT-engaging hole 404. Those details are all similar to corresponding details of the test plate 300. The major difference is that the upper layer 406 includes first, second, and third sub-layers 406A, 406B, and 406C such that sub-layers 406A and 406C are electrically nonconductive and sub-layer 406B is electrically conductive so that it can function as a guard layer.

[0036] Thus, the invention provides a test plate that achieves more function, efficiency, and/or cost reduction. Although exemplary embodiments have been shown and described, one of ordinary skill in the art may make many changes, modifications, and substitutions without necessarily departing from the spirit and scope of the invention. 

What is claimed is: claims
 1. A test plate, comprising: a DUT-holding plate having an upper side, a lower side, and a rotational axis; the DUT-holding plate defining a plurality of DUT-engaging holes that extend through the DUT-holding plate from the upper side to the lower side; each of said DUT-holding holes having a central axis that extends between the upper side and the lower side; and each of said DUT-engaging holes being so disposed that the central axis of each DUT-engaging hole is not parallel to the rotational axis.
 2. A test plate as recited in claim 1, wherein the central axes of the plurality of DUT-engaging holes are inclined outwardly from the upper surface toward the rotational axis.
 3. A test plate as recited in claim 1, wherein the central axes of the plurality of DUT-engaging holes are inclined relative to the rotational axis angles that have sizes within a range of one degree to eighty-nine degrees.
 4. A test plate as recited in claim 1, wherein the DUT-holding plate has at least two layers that are bonded together to form the DUT-holding plate.
 5. A test plate as recited in claim 4, wherein the DUT-holding plate has at least one conductive layer composed of an electrically conductive material in order to enable use of the conductive layer as a guard layer for electrical testing purposes has at least two layers.
 6. A test plate for use atop a vacuum plate portion of a component testing system, the test plate comprising: an upper layer and a lower layer that are bonded together to form a DUT-holding plate having an upper side, a lower side, and a rotational axis; the DUT-holding plate defining a plurality of DUT-engaging holes that extend through the DUT-holding plate from the upper side to the lower side; the upper layer defining an upper section of each of the DUT-engaging holes that provides a close fit for a DUT; and the lower layer defining a lower section of each of the DUT-engaging holes and a plurality of vacuum passageways that function as means for coupling a vacuum source from the vacuum plate portion of the component testing system to the plurality of DUT-engaging holes.
 7. A test plate as recited in claim 6, wherein: the lower layer includes first and second lower sub-layers that are bonded together to form the lower layer; the first lower sub-layer defines a first segment of the lower section of each DUT-engaging hole and a first segment of each vacuum passageway; and the second lower sub-layer defines a second segment of the lower section of each DUT-engaging hole that provides a close fit for a DUT in order to help support the DUT, while also defining a second segment of each vacuum passageway such that the second segments of the vacuum passageways are spaced apart from the DUT-engaging holes.
 8. A test plate as recited in claim 6, wherein the upper layer of the DUT-holding plate has at least one conductive upper sub-layer composed of an electrically conductive material in order to enable use of the conductive upper sub-layer as a guard layer for electrical testing purposes.
 9. A method for fabricating a DUT-holding plate, the method comprising: providing upper and lower DUT-holding plate layers such that the upper and lower DUT-holding plate layers have DUT-engaging holes and vacuum passageways formed in them; and bonding the upper and lower DUT-holding plate layers together to form a DUT-holding plate. 